StdpC: a modern dynamic clamp

With the advancement of computer technology many novel uses of dynamic clamp have become possible. We have added new features to our dynamic clamp software StdpC (“Spike timing-dependent plasticity Clamp”) allowing such new applications while conserving the ease of use and installation of the popular earlier Dynclamp 2/4 package. Here, we introduce the new features of a waveform generator, freely programmable Hodgkin–Huxley conductances, learning synapses, graphic data displays, and a powerful scripting mechanism and discuss examples of experiments using these features. In the first example we built and ‘voltage clamped’ a conductance based model cell from a passive resistor–capacitor (RC) circuit using the dynamic clamp software to generate the voltage-dependent currents. In the second example we coupled our new spike generator through a burst detection/burst generation mechanism in a phase-dependent way to a neuron in a central pattern generator and dissected the subtle interaction between neurons, which seems to implement an information transfer through intraburst spike patterns. In the third example, making use of the new plasticity mechanism for simulated synapses, we analyzed the effect of spike timing-dependent plasticity (STDP) on synchronization revealing considerable enhancement of the entrainment of a post-synaptic neuron by a periodic spike train. These examples illustrate that with modern dynamic clamp software like StdpC, the dynamic clamp has developed beyond the mere introduction of artificial synapses or ionic conductances into neurons to a universal research tool, which might well become a standard instrument of modern electrophysiology

A Novel Neural Substrate for the Transformation of Olfactory Inputs into Motor Output

Anatomical and physiological experiments in the lamprey reveal the neural circuit involved in transforming olfactory inputs into motor outputs, which was previously unknown in a vertebrate

Chemical cues and pheromones in the sea lamprey (Petromyzon marinus)

Chemical cues and pheromones guide decisions in organisms throughout the animal kingdom. The neurobiology, function, and evolution of olfaction are particularly well described in insects, and resulting concepts have driven novel approaches to pest control. However, aside from several exceptions, the olfactory biology of vertebrates remains poorly understood. One exception is the sea lamprey (Petromyzon marinus), which relies heavily upon olfaction during reproduction. Here, we provide a broad review of the chemical cues and pheromones used by the sea lamprey during reproduction, including overviews of the sea lamprey olfactory system, chemical cues and pheromones, and potential applications to population management. The critical role of olfaction in mediating the sea lamprey life cycle is evident by a well-developed olfactory system. Sea lamprey use chemical cues and pheromones to identify productive spawning habitat, coordinate spawning behaviors, and avoid risk. Manipulation of olfactory biology offers opportunities for management of populations in the Laurentian Great Lakes, where the sea lamprey is a destructive invader. We suggest that the sea lamprey is a broadly useful organism with which to study vertebrate olfaction because of its simple but well-developed olfactory organ, the dominant role of olfaction in guiding behaviors during reproduction, and the direct implications for vertebrate pest management

Plateau potentials and membrane oscillations in parasympathetic preganglionic neurones and intermediolateral neurones in the rat lumbosacral spinal cord

Whole-cell patch recordings were made from parasympathetic preganglionic neurones (P-PGNs) and unidentified intermediolateral (IML) neurones in thick slices of the lower lumbar and sacral spinal cord of 14- to 21-day-old rats. The P-PGNs and IML neurones examined were similar in terms of soma sizes, input resistance and capacitance, and displayed a sag conductance as well as rebound firing. In the absence of drugs, the neurones responded with either tonic or adapting firing to depolarizing current steps. However, in the presence of the group I metabotropic glutamate receptor agonist (RS)-3,5-dihydroxyphenylglycine (DHPG), almost half of the neurones displayed accelerating firing rates during the constant current injection, followed by a sustained after-discharge. In the presence of TTX, plateau potentials were observed. The firing changes and plateaux were blocked by nifedipine, an L-type Ca(2+) channel blocker, and (S)-(−)-Bay K8644 was able to produce these firing changes and plateaux in the absence of DHPG, demonstrating the involvement of an L-type Ca(2+) conductance. Ca(2+)-activated nonspecific cationic conductances also appear to contribute to the firing changes. A few neurones displayed membrane oscillations and burst firing in the presence of DHPG. The results suggest that the firing characteristics of both P-PGNs and other neurones likely to be involved in caudal spinal reflex control are not static but, rather, quite dynamic and under metabotropic glutamate receptor modulatory control. Such changes in firing patterns may be involved in normal pelvic parasympathetic reflex function during micturition, defaecation and sexual reflexes, and may contribute to the abnormal output patterns seen with loss of descending brainstem input and visceral or perineal sensory disturbances

GABAergic modulation of olfactomotor transmission in lampreys.

Odor-guided behaviors, including homing, predator avoidance, or food and mate searching, are ubiquitous in animals. It is only recently that the neural substrate underlying olfactomotor behaviors in vertebrates was uncovered in lampreys. It consists of a neural pathway extending from the medial part of the olfactory bulb (medOB) to locomotor control centers in the brainstem via a single relay in the caudal diencephalon. This hardwired olfactomotor pathway is present throughout life and may be responsible for the olfactory-induced motor behaviors seen at all life stages. We investigated modulatory mechanisms acting on this pathway by conducting anatomical (tract tracing and immunohistochemistry) and physiological (intracellular recordings and calcium imaging) experiments on lamprey brain preparations. We show that the GABAergic circuitry of the olfactory bulb (OB) acts as a gatekeeper of this hardwired sensorimotor pathway. We also demonstrate the presence of a novel olfactomotor pathway that originates in the non-medOB and consists of a projection to the lateral pallium (LPal) that, in turn, projects to the caudal diencephalon and to the mesencephalic locomotor region (MLR). Our results indicate that olfactory inputs can induce behavioral responses by activating brain locomotor centers via two distinct pathways that are strongly modulated by GABA in the OB. The existence of segregated olfactory subsystems in lampreys suggests that the organization of the olfactory system in functional clusters may be a common ancestral trait of vertebrates

Glutamate injection into the OB induces fictive locomotion.

<p>(A) Top trace: Intracellular recording of a RS cell. Note the large excitation induced by the injection of 3 mM glutamate in the ipsilateral OB. Bottom traces: Ventral root (VR) discharges on both sides. (B) Detail from the boxed area in (B) shows fictive locomotion characterized by alternating ipsilateral and contralateral ventral root activity (iVR and cVR, respectively). Note that the RS cell shows rhythmic oscillations in tune with the fictive locomotor pattern.</p